AHT20温湿度传感器，读取数据结果如何转换？

    uint32_t humiRaw = buffer[1];
    humiRaw = (humiRaw << 8) | buffer[2];
    humiRaw = (humiRaw << 4) | ((buffer[3] & 0xF0) >> 4);
    *humi = humiRaw / (float)AHT20_RESLUTION * 100;

    uint32_t tempRaw = buffer[3] & 0x0F;
    tempRaw = (tempRaw << 8) | buffer[4];
    tempRaw = (tempRaw << 8) | buffer[5];
    *temp = tempRaw / (float)AHT20_RESLUTION * 200 - 50;

能不能详细解释一下以上加粗部分，是什么意思？为什么要这样做？

整个函数如下：

// 接收测量结果，拼接转换为标准值
uint32_t AHT20_GetMeasureResult(float* temp, float* humi)
{
    uint32_t retval = 0, i = 0;
    if (temp == NULL || humi == NULL) {
        return WIFI_IOT_FAILURE;
    }

    uint8_t buffer[AHT20_STATUS_RESPONSE_MAX] = { 0 };
    memset(&buffer, 0x0, sizeof(buffer));
    retval = AHT20_Read(buffer, sizeof(buffer));  // recv status command result
    if (retval != WIFI_IOT_SUCCESS) {
        return retval;
    }

    for (i = 0; AHT20_STATUS_BUSY(buffer[0]) && i < AHT20_MAX_RETRY; i++) {
        // printf("AHT20 device busy, retry %d/%d!\r\n", i, AHT20_MAX_RETRY);
        usleep(AHT20_MEASURE_TIME);
        retval = AHT20_Read(buffer, sizeof(buffer));  // recv status command result
        if (retval != WIFI_IOT_SUCCESS) {
            return retval;
        }
    }
    if (i >= AHT20_MAX_RETRY) {
        printf("AHT20 device always busy!\r\n");
        return WIFI_IOT_FAILURE;
    }

    uint32_t humiRaw = buffer[1];
    humiRaw = (humiRaw << 8) | buffer[2];
    humiRaw = (humiRaw << 4) | ((buffer[3] & 0xF0) >> 4);
    *humi = humiRaw / (float)AHT20_RESLUTION * 100;

    uint32_t tempRaw = buffer[3] & 0x0F;
    tempRaw = (tempRaw << 8) | buffer[4];
    tempRaw = (tempRaw << 8) | buffer[5];
    *temp = tempRaw / (float)AHT20_RESLUTION * 200 - 50;
    // printf("humi = %05X, %f, temp= %05X, %f\r\n", humiRaw, *humi, tempRaw, *temp);
    return WIFI_IOT_SUCCESS;
}